The present invention relates to an improved reactive for determining the iron content and the overall iron-binding capacity of biological liquids, in particular of serum.
In 1979, Garcic in Clin. Chim. Acta. 94; 115-119 (1979), resuming a study carried out in 1969 by Shijo et al. in Jap. Analyst. (17); 1519-1523 (1968), devised a reagent for determining sideremia and the iron-binding capacity of serum (TIBC) containing the chromogenic chromazurol B (Cab) which, by reacting with iron, yields a compound with a high molar extinction at 630 nm (A630=1.6.times.10.sup.5 l/mol cm).
Subsequently, Tabacco et al. in 1981 in Clin. Chim. Acta. 114; 287-289 (1981), modified the reagent, replacing the sodium chloride with magnesium chloride, which allowed a greater recovery.
All these reagents were not free from disadvantages, which mainly lied in the interference of proteins and to a lesser extent in the presence of Cu.sup.+2 in the serum, which biased the result of the analysis.
For this reason, the process employed with these reagents entailed the performing of blank sample, with obvious difficulties and disadvantages for the user.
In 1981, Brega, in the Italian patent application No. 20859 A/81, described a reagent, again containing the chromogenic chromazurol B, which was suitable for determining the iron and TIBC in the serum without a blank sample.
However, this reagent was also not free from the proteic and ionic interferences; the increase in color due to the interfering substances was simply compensated by the inability to extract and meter all the iron present in the serum.
Obviously these factors are variable, so that the reagent is inadequate to yield accurate results.